The FBI’s initial analysis says the 15 devices Cesar Sayoc mailed to more than a dozen high-profile critics of President Donald Trump contained “shards of glass that could only have been intended to maximize harm to the defendant’s victims” as well as material with explosive qualities.

Sayoc, 56, was taken into custody in Florida last week and charged in connection with the series of pipe bombs sent through the mail and by courier. Sources have told NBC news he had a list of more than 100 potential targets.